In general, at least one printed circuit board (PCB) is provided in an electronic device. On such printed circuit board, devices having a variety of shapes are mounted. For inspecting defects or the like of such devices, a three-dimensional shape measuring apparatus is typically used.
In a conventional three-dimensional shape measuring apparatus, light is irradiated on a measurement target object such as a PCB. A reflective image of the measurement target object is then captured using a camera. Then, a three-dimensional shape based on the height of the measurement target object is measured using the reflective image thus captured.
The measuring apparatus includes an illumination unit that provides light toward the measurement target object and a camera that captures an image of the measurement target object using the reflective light reflected from the measurement target object. In the apparatus, the camera includes an image formation lens through which the reflective light passes. The camera captures the image of the measurement target object by receiving the reflective light that has passed through the image formation lens.
FIGS. 1A and 1B are configuration diagrams of a conventional three-dimensional shape measuring apparatus. Referring to FIGS. 1A and 1B, an illumination unit 1 irradiates light on a measurement target object via a beam splitter 2. The light reflected from the measurement target object travels toward an imaging unit 7 via an objective lens 3, an aperture 4, an image formation lens 5, and a pinhole 6. A control unit 8 moves the imaging unit 7 along a z-axis (in a direction normal to a substrate) so that an image captured by the imaging unit 7 is in focus. As shown in FIGS. 1A and 1B, when measurement target objects have different heights h1 and h2, the image formation positions of the measurement target objects differ from each other. Therefore, according to a conventional method, the height of a measurement target object is measured while changing the position of the imaging unit 7 with the control unit 8. In FIGS. 1A and 1B, the imaging unit 7 needs to be moved by distance d according to a height difference h1−h2.
In a three-dimensional shape measuring apparatus according to such conventional method, a height measurement can be carried out by a height measuring unit when an image captured by the imaging unit is in focus. To this end, the imaging unit has to move along a z-axis according to the height of a measurement target object before scanning the measurement target object. This poses a problem in that when measuring a three-dimensional shape of a measurement target object, an x, y, and z-axes scan is necessary.
A three-dimensional shape measuring apparatus according to a conventional method is disclosed in Korean Patent Application Publication No. 10-2011-0086222.